长江口及东海赤潮海洋环境特征综合探讨

针对我国东海及长江口邻近海域赤潮频繁发生的现象,本文通过大量文献查阅和研究追踪,分别从东海赤潮的生物化学、物理海洋和地质沉积三大方面对其爆发的海洋环境特征进行了综合研究。具体涉及浮游藻类密度、叶绿素a含量、初级生产力、海洋温盐流、地貌沉积八个分项的解释,从整体上对长江口及东海赤潮生消演变的海洋环境进行了初步的探讨,为进一步的认识赤潮提供了研究基础。     

风浪作用下太湖改性沉积物对藻体絮凝去除效果研究

以壳聚糖改性的太湖原位沉积物为分散介质,应用Y-型再悬浮发生装置,通过定量模拟太湖常见的中等级别风情,研究再悬浮作用下,改性沉积物对蓝藻水华的絮凝去除作用.结果表明,在黏土加入量为0.2　g·L^-1,壳聚糖分别为0.100和0.150　g·L^-1,其蓝藻的去除率分别为93.55%和99.19%;在静止30 min后,壳聚糖加入量为0.15 　g·L^-1时,水体的浊度去除率达到78.60%;静止8 h后,水体的浊度去除率达到93.88%.同时,短期内壳聚糖的加入对水体中PO^3-₄-P有一定的去除作用.初步结果表明,在中风风情下,壳聚糖的加入量为0.15　g·L^-1时,能更有效地去除蓝藻.表明利用壳聚糖改性沉积物来絮凝沉降太湖水华藻体,具有较好的应用前景.对比研究表明,引入水动力强度和水柱高度定量模拟方法,在确定壳聚糖投加量絮凝除藻中,具有明显的方法优势.     

三峡水库支流大宁河冬、春季水华调查研究

以三峡水库主要支流--大宁河冬、春季2次不同类型水华的调查数据为依据,分析并比较了不同水华期间水质的变化、营养盐的构成及水华的特征.结果表明,大宁河冬季水华以唐家湾为中心,叶绿素a(Chl-a)含量较高[(Chl-a)_(max)/(Chl-a)_(min)=260];随着藻类的生长总氮(TN)、总磷(TP)和高锰酸盐指数出现富集而含量升高,溶解氧(DO)和pH却出现低值;水华高峰期水体藻类较少,共发现2门4种,水华优势种为铜绿微囊藻和水华微囊藻,藻密度高达3.15×10~7个/L,相关加权综合营养状态指数为80,属于重度富营养化水体.而春季水华属于自回水段以下整体性暴发,Chl-a含量也较高[(Chl-a)_(max)/(Chl-a)_(min)=140];TN、TP和高锰酸盐指数均是随着水华的发生逐渐升高;水华高峰期藻类种群丰富,共发现5门44种,各断面水华优势种和藻密度均不同,相关加权综合营养状态指数显示东坪坝和白水河为轻度富营养化水体.相关性分析表明,冬季水华期间Chl-a与TN、TP、高锰酸盐指数、水温呈显著正相关,与DO、透明度(SD)呈显著负相关;春季水华Chl-a与TP、高锰酸盐指数、DO、pH呈显著正相关,与SD呈显著负相关.冬季水华pH与SD呈显著正相关,与TN、TP、高锰酸盐指数呈显著负相关;而春季水华pH与Chl-a、TP、高锰酸盐指数、DO、气温呈显著正相关,与SD呈显著负相关.     

Fe~(3+)对不同进水氮磷比藻塘水质净化效果研究

铁是动植物进行生命活动不可缺少的元素。在藻塘内,铁能够影响藻细胞生长与繁殖,影响水质净化效果。通过研究不同浓度Fe3+对小球藻生长影响,并设定进水C/N和N/P,确定适宜Fe3+对藻塘出水理化性质及其污染物去除的影响。结果表明:当c(Fe3+)为10 000 nmol/L时,藻细胞质量增加约25%。适宜浓度Fe3+可调节藻塘水体DO、p H及ORP,提高净化效果。Fe3+利用率与COD、TN和TP去除率呈线性正相关,且随进水N/P的提高而增高。当ρ(N)/ρ(P)为50,ρ(C)/ρ(N)=5时,加铁藻塘COD、TN、TP去除率分别为45.34%、77.14%、43.11%,与未加铁藻塘相比,去除率分别提高约3,5.47,9.64个百分点。因此,铁可以促进藻类的生长,当藻塘进水ρ(C)∶ρ(N)∶ρ(P)∶ρ(Fe)为250∶50∶5∶1时,可降低污染物浓度,提高去除效果。     

水库大型围隔放养鲢鱼、鳙鱼控藻的研究

为减轻水源地水华的发生,在天津于桥水库建立了10个300m2大型围隔,分别放养密度为0,10,30,60g/m3的鲢鱼、鳙鱼进行控藻试验.结果表明,无鱼围隔内的蓝藻比例上升并形成微囊藻水华,各有鱼围隔内蓝藻比例始终保持在低位水平.与此同时,鲢鱼、鳙鱼的滤食导致小型藻类的大量增长进而造成藻类总生物量及叶绿素a不同程度地升高.由此可知,鲢鱼、鳙鱼适用于控制蓝藻水华而非藻类总量.     

A remote sensing tool for near real-time monitoring of harmful algal blooms and turbidity in reservoirs

Harmful algal blooms (HABs) diminish the utility of reservoirs for drinking water supply, irrigation, recreation, and ecosystem service provision. HABs decrease water quality and are a significant health concern in surface water bodies. Near real-time monitoring of HABs in reservoirs and small water bodies is essential to understand the dynamics of turbidity and HAB formation. This study uses satellite imagery to remotely sense chlorophyll-a concentrations (chl-a), phycocyanin concentrations, and turbidity in two reservoirs, the Grand Lake O′ the Cherokees and Hudson Reservoir, OK, USA, to develop a tool for near real-time monitoring of HABs. Landsat-8 and Sentinel-2 imagery from 2013 to 2017 and from 2015 to 2020 were used to train and test three different models that include multiple regression, support vector regression (SVR), and random forest regression (RFR). Performance was assessed by comparing the three models to estimate chl-a, phycocyanin, and turbidity. The results showed that RFR achieved the best performance, with R² values of 0.75, 0.82, and 0.79 for chl-a, turbidity, and phycocyanin, while multiple regression had R² values of 0.29, 0.51, and 0.46 and SVR had R² values of 0.58, 0.62, and 0.61 on the testing datasets, respectively. This paper examines the potential of the developed open-source satellite remote sensing tool for monitoring reservoirs in Oklahoma to assess spatial and temporal variations in surface water quality.     

改性黏土絮凝海洋原甲藻对水体中氮、磷的影响研究

通过对比研究典型有害微藻海洋原甲藻(Prorocentrum micans Ehrenberg)自然消亡(A1组)及改性黏土絮凝(A2组)两种体系,考察两体系中氮、磷等主要水质因子的变化情况.结果表明,改性黏土能有效去除P. micans并影响其后期生长状态,0.4g/L改性黏土添加3.5h后去除率可达60%以上,且藻密度无二次增长.改性黏土絮凝藻华过程中能有效去除水体营养元素, A2组DIP和DIN较A1组分别降低85%和35%.另外,添加改性黏土对水体有机氮、磷影响值得关注,第33d A2组TON和TOP较A1组分别减少约120, 6μmol/L. 改性黏土对有机氮、磷存在一定的埋存保护作用,通过吸附絮凝、螯合等作用使有机氮、磷脱离水体系统,而自然消亡体系中的微藻消亡后将通过分解、矿化等过程快速进入水体参与再循环.该研究系统阐述了改性黏土絮凝P. micans对水体营养环境的影响,以期为现场治理提供理论支持.     

Comparison of growth and lipid accumulation properties of two oleaginous microalgae under different nutrient conditions

This study compared the growth and lipid accumulation properties of two oleaginous microalgae, namely, Scenedesmus sp. LX1 and Chlorella sp. HQ, under different nutrient conditions. Both algal species obtained the highest biomass, lipid content and lipid yield under low-nutrient conditions （mBGll medium）. The biomass, lipid content and lipid yield of Scenedesmus sp. LX1 were 0.42g·L^-1, 22.5% and 93.8mg·L^-1, respectively. These values were relatively higher than those of Chlorella sp. HQ （0.30g·L^-1, 17.1% and 51.3mg·L^-1, respectively）. These algae were then cultivated in an SE medium that contained more nutrients; as a result, the biomass and lipid yield of Scenedesmus sp. LX1 reduced more significantly than those of Chlorella sp. HQ. Opposite results were observed in lipid and triacylglycerols （TAGs） contents. The cell sizes of both algal species under low-nutrient conditions were larger than those under high-nutrient conditions. Chlorella sp. HQ cells did not aggregate, but Scenedesmus sp. LX1 cells flocculated easily, particularly under low-nutrient conditions. In summary, low-nutrient conditions favour the growth and lipid production of both algae, but Scenedesmus sp. LX1 outperforms Chlorella sp. HQ.     

南水北调工程实施后汉江水华发生可能性研究

南水北调中线工程对汉江中下游的生态与环境影响已有大量的研究成果,特别是对水华问题进行了更为深入的研究,但是其研究主要集中于仙桃至河口段,而沙洋以上河段还未进行过水华方面的研究工作。鉴于1998年及2003年两次发生的水华事件影响范围都达沙洋以上河段(已达湖北钟祥河段),以及南水北调中线工程实施后汉江河道流量减小,流速降低,水环境容量降低,特别是兴隆枢纽回水区的壅水作用使其水体流速大幅下降(经计算小于0.3 m/s),再加上汉江中下游水体中总氮、总磷含量普遍偏高,对兴隆枢纽回水区及襄樊市区段水华发生可能性分别应用加权灰关联度以及模糊数学中的隶属度概念进行了计算评价,得出结论为：在维持污染现状情况下兴隆枢纽回水区在枯水期(505.7 m\+3/s流量)具备水华事件发生的水文及营养物质条件;到2020年襄樊市区段也将具备水华事件发生的水文及营养物质条件。     

Toxicity of cadmium to the green alga Parachlorella kessleri: Producing Cd-loaded algae for feeding experiments

The effects of Cd at environmental concentrations (0–32 µg/L) on the green alga Parachlorella kessleri were investigated. At about 3 µg Cd/L, toxic effects of Cd are becoming evident, much lower than reported previously. At 8 µg/L and higher, pronounced adverse effects on growth, cell morphology, size, and physiological state are seen. Therefore, levels lower than 2 µg Cd/L should be employed to produce Cd-carrying algae for feeding experiments with organisms on the next trophic level, e.g. mussels, to avoid reduced food uptake. These findings also suggest that aquatic ecosystem conditions can be indirectly influenced via the impairment of the nutritional value of algae since they are the basic organisms of aquatic food chains.